The invention relates to a method for vibration damping of a drive train comprising an internal combustion engine which has an engine torque applied to a crankshaft, an electric machine, a transmission with a transmission input shaft, and a torque transmission device arranged between the crankshaft and the transmission input shaft, which torque transmission device has at least one flywheel mass capable of vibrating with a moment of inertia and a state controller for controlling the electric machine by a compensation torque compensating for torsional vibrations at the transmission input shaft.
Drive trains with an internal combustion engine and an electric machine are known as hybrid drive trains, in which an internal combustion engine and/or an electric machine contribute torque to drive the vehicle. In such drive trains the internal combustion engine and the electric machine are coupled to each other via a mechanical interface and respectively transfer the applied motor torque (internal combustion engine) and the operating torque (electric machine) via a transmission input shaft to a transmission and from there to the driving wheels. Furthermore, a torque transmission device is provided between the crankshaft of the internal combustion engine and the transmission input shaft, which for example damps torsional vibrations as a torsional vibration damper, can couple and decouple the crankshaft from the transmission input shaft as a friction clutch, and/or transfer the motor torque in some other fashion to the transmission input shaft. Furthermore, the torque transmission device may be coupled in a torque-proof fashion to a rotor of the electric machine at the input side or the output side.
The internal combustion engine is subject to torsional vibrations due to its effective principle, with the drive train and the vehicular body generating the vibrations potentially leading to loss in comfort inside the vehicle, which vibrations are counteracted in a manner known per se via torsional vibration damping devices, such as torsional vibration compensators, flywheel pendulums, or the like. Additionally, rapid changes, for example jumps in the torque of the electric machine or the internal combustion engine, can trigger arbitrary resonance frequencies in the drive train. Therefore, from DE 10 2011 084 548 A1 an active vibration control is known for a hybrid vehicle, in which a reduced drive train model is used.